Solar Energy Collection Devices

ABSTRACT

Devices and methods for collecting solar energy using photovoltaic material are disclosed.

PRIORITY STATEMENT

This application is a divisional application to Non-Provisionalapplication Ser. No. 12/235,376, filed on Sep. 22, 2008 which claims thebenefit of U.S. Provisional Application No. 61/052,117 filed May 9, 2008and U.S. Provisional Application No. 61/088,967 filed Aug. 14, 2008.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to devices and methods for the collection ofsolar energy using a photovoltaic solar cell.

2. Background and Description of the State of the Art

FIGS. 1A-1B illustrates a conventional construction for photovoltaic(PV) cells, e.g., a solar cell, which converts light energy toelectricity. In this example, the cell 1 is generally square-like withan upper surface 2 corresponding to a sun-receiving or sun-facing side 2of the solar cell 1. The opposing surface 3 faces away from thedirection of sunlight. In this example, the solar cell 1 has an n-typedoped silicon layer and p-type doped silicon layer separated by ajunction layer. The sun-facing side 2 has a surface area made up of thePV material, e.g., n-type doped silicon, and contacts 5 for conducting acurrent when the PV material receives light energy. The contacts 5 arein the shape of lengthwise conducting lines 5 a and two central buses 5b for collecting charge from the conducting lines 5 a. The central buses5 b, and the corresponding electrode 5 c for collecting a positivecharge, are electrically connected to adjacent solar cells (preferably,a parallel connection) to form a solar cell module. Several modulesconnected together form a solar cell panel or solar panel.

A photovoltaic power system may have a single solar cell module orpanel, or multiple modules/panels connected by combinations of seriesand parallel circuits as a photovoltaic array, or solar array. In thecase of a single module system producing AC power output, the solar cellmodule may be connected to an inverter or load through a junction boxthat incorporates a fuse to protect the photovoltaic module if backfeeding from a power utility or a battery might occur. Solar cellmodules may be configured either with a frame or without a frame. Aframeless solar cell module is generally referred to as a laminate.Examples of power systems having interconnected solar modules or panelsmay be found in U.S. Pub. No. 2003/0111103.

In recent years efforts are being made to develop thin-film PV material.Some such types of material are a-Si, CdTe, and CIGS. At present, thesesolutions have an efficiency rating of about 10% in commerciallyavailable panels (in laboratory conditions CIGS has been shown to be upto about 20% efficient). some of these thin-film technologies sufferfrom degradation and loss of efficiency over time. Presently, singlecrystalline PV, and to some extent poly-Si (although not as efficient),offer highest efficiency as a long-term proven technology.

Concentrated photovoltaics (CPV) utilize lenses or minors to focus, orconcentrate solar energy onto PV material. Low concentrators, e.g.,2.times. concentrators, can require no tracking or movement (e.g.,linear Winston collectors). These concentrators often times need to beorientated in an East-to-West orientation and tilted towards thecelestial equator which may not be easily accomplished given theavailable mounting locations. Additionally, these concentrators can beexpensive to manufacture because they use non-standard shapes for thelenses, e.g., Winston collectors. High concentrators need active movingparts in two dimensions and active cooling of the PV cells.

A “concentrator” is intended to mean a device that concentratesreflected and/or refracted light for the purposes of increasing thesolar flux onto PV material. Unless otherwise noted, when a “lens” or“lenses” is/are referred to, it carries the same meaning as aconcentrator, i.e., intended to focus or concentrate solar energy. A“linear”, “one-dimensional” or “1-D” concentrator is intended to mean aconcentrator configured for focusing light in only one-dimensions. Oneexample of a 1-D concentrator is a rod lens. A “two-dimensional” or“2-D” concentrator is intended to focus light in two dimensions. Aspherical lens is one example of a 2-D concentrator. A 1-D concentratorhas a “line of focus”, which is intended to mean the line or strip offocused light over the length of the concentrator. A line of focus for a1-D concentrator, oriented east to west, changes during the course ofthe year. Thus, for a 1D concentrator at the Earth's equator and pointedat the celestial equator at equinox, the line of focus is parallel tothe lens. At the periods of solstice the line of focus is distancedfarthest from this condition. Throughout the discussion, reference maysometimes be made to a solar panel, module or solar collection system.One of ordinary skill would appreciate that the terms ‘solar panel’ or‘solar module’ do not necessarily limit the scope of the disclosure.Unless otherwise apparent, the disclosure applies to any solarcollection device that utilizes concentrators to focus light onto PVmaterial in accordance with the foregoing objectives.

A “tracking panel” is intended to mean a panel that is maintained toface the sun such that light rays are always orientated normal to thepanel surface. A tracking panel may be rotated so that solar rays arealways directed normal to the surfaces having PV material. Accordingly,the effective area, A.sub.EFF for a tracking panel is intended to alwaysbe equal to the corresponding surface area A.sub.PV of the panel. For apanel that does not track the sun's motion A.sub.EFF<A.sub.PV wheneverthe sun's apparent position changes from the position that the panelfaces. For a fully tracked panel (as opposed to a partially trackedpanel, e.g., partial tracking when rotation about only one axis as thesun changes its position in the sky) the acceptance angle is of lesseror no importance to a design because the panel is being tracked. For apartially tracked panel, e.g., when linear concentrators rotate abouttheir longitudinal axes, the acceptance angle requirements reduce toonly one dimension: the longitudinal dimension. Therefore, a linearconcentrator is designed such that it provides a very large acceptanceangle along its longitudinal direction so that there would be no need tomove them, or the panel, in that direction.

For solar panels that use concentrators, “acceptance angle” means theangle beyond which not all focused or collected light is received on PVmaterial. A CPV panel that does not track the sun but still collects sunlight from morning to evening throughout the year (hereafter refer to aspanels that increase the acceptance angle) does this in a few ways. Itcan be made of smaller units, such as linear Winston collectors, wherethe acceptance angle is designed into each collector. With such a designthe CPV panel is oriented usually in an East-to-West direction andtilted towards the celestial equator. A CPV panel can also collectsunlight without tracking by incorporating moving parts within thepanel, while the panel remains stationary, such as moving minors thatfocus light onto their corresponding focal points where a PV cell ispositioned.

A solar panel's “collection plane” is intended to refer to the planewhere the PV material is generally located to receive solar flux. Forexample, a two-axis tracking solar panel is configured to be rotatedabout two orthogonal axes that lie within the collection plane (x and yaxes depicted in FIG. 8A). With reference to FIG. 7 the vector Pnextends normal to the collection plane for the panel shown.

SUMMARY OF THE INVENTION

The invention is directed to devices, methods, systems and apparatus forimproving solar energy collection, reducing costs associated withmanufacture of solar energy collection and improving the versatility andsimplicity of solar collection devices. The methods and apparatusdisclosed herein may provide a number of solutions to the high demand,but limited supply for photovoltaic (“PV”) material, especiallyhigh-efficiency PV material for converting solar energy to electricalenergy.

According to one aspect of the invention, a collection device includes aseries of glass (or other transparent material) rods, e.g., rods with acircular cross section, that are arranged parallel and side by side toeach other. Each rod acts as a linear lens having, e.g., approximately a5 to 1 concentration ratio when standard glass is used and the PVmaterial is attached directly to the rod lenses. The rods can have alarger or smaller concentration ratio depending on the index ofrefraction of the material. Tracking may or may not be used. In someembodiments, tracking may not be necessary. Instead, the collectiondevice may be rotated about a single axis normal to the panel, therebyrotating all rods simultaneously to allow collection of solar energy. Insome embodiments, a minimal movement may be achieved by rotation of eachrod lens about its longitudinal axis within the panel, thereby allowingthe collection of solar energy as the sun's apparent position changes.Other aspects of the disclosure which can be practiced in view of thedisclosure: no requirement for active cooling of the PV cells and norequirement for installation at an angle or orientation, therebyallowing a solar collection device to be more easily deployed; the samefootprint as conventional panels; a higher efficiency than a flat panel(assuming the same type of PV material is used). In some embodiments, asolar collection device may be self installed, which offers theadvantage of dramatically decreasing the installation cost (up to about50%), as will be apparent from the disclosure. In other embodiments, apanel containing the rod lenses can be tracked on a 1D tracking platformwithout the need for each individual rod lens to rotate. In otherembodiments, the cross section of the rod lenses can be elliptical orany other shape.

According to one aspect of the disclosure, rod lenses are used tocollect solar energy onto a strip of PV material. According to theseembodiments, the PV material may be affixed to the rod lenses and therod lenses rotated about their longitudinal axis (or the panel axis) tofollow the sun. When the PV material is affixed to the rods, the PVmaterial may be made separately, then affixed to the rods using, e.g.,an index-matching adhesive, or formed on the rods, e.g., by chemicalvapor deposition, evaporation, electroplating, or other suitablemanufacturing techniques. In terms of assessing the efficiency of acollector using rod lenses according to the disclosure, it is estimatedthat about 7% efficiency is lost due to reflection. However, as comparedto a flat panel, rod lenses made of standard glass may have anapproximate 5 to 1 concentration ratio, which provides about a 10% gainin efficiency over a flat panel using the same PV material. The combinedeffect, i.e., loss due to reflection (due to the curved lens surface)+5to 1 concentration ratio, means a solar collector according to thedisclosure is able to achieve the same, or in some cases a higher levelof efficiency but with a lower manufacturing cost and in some casesinstallation cost. A rod lens may have a simple shape, e.g.,cylindrical, which provides costs advantages because this structure isreadily available at high volumes from most glass manufacturers. Acircular cross-section rod lens may be desirable when collecting solarenergy by rotating each rod because the lens is rotationally symmetric.Thus, when collecting solar energy by rotating lenses about theirlongitudinal axes, the individual lenses can be packed together closelywithout interface from neighboring rods.

According to another aspect of the disclosure, PV cell strips may beseparated from the rod lenses so that there is a finite distance betweenthe lens and PV cell strips. In these embodiments, the strips can beaffixed to a separate plate and the rod lenses to another plate. The twoplates may then be moved with respect to each other to keep the PV cellstrips in focus.

Solar collection devices of the foregoing type may be utilized for rooftop power generation and commercial-scale power generation, in whichcase the entire panel may or may not be tracked. Solar collectiondevices according to the disclosure may also be constructed as “curtain”applications in high rise buildings or integrated inside windows.

The following conventions/definitions are adopted. Movement of the sunduring the day and over the course of the year means the apparenteast-west and north-south motion, respectively, of the sun across thesky. For convenience of description, an apparent longitudinal andlatitudinal motion of the sun is adopted, and intended to mean the dailyand yearly apparent motion of the sun, respectively. Thus, thelongitudinal motion of the sun over a single day is intended to mean theeast-to-west apparent motion of the sun over a path that corresponds tothe intersection of the celestial sphere and the ecliptic plane for thatday. And the latitudinal motion of the sun over the year is intended tomean the movement of this path on the celestial sphere over the courseof a year. Thus, for an observer located at the earth's equator, thelongitudinal apparent path of the sun over the celestial sphere at theautumn or spring equinox passes directly overhead. Over the course ofthe year, this apparent path changes and reaches its maxima change inposition from the spring/autumn equinox at the winter/summer solstices(.+−.23.5 degree latitudinal change). Thus, over the course of a yearthe sun has an apparent “latitudinal” motion or change in position andover the course of a day the sun has an apparent “longitudinal” motionor change in position.

In accordance with the foregoing objectives, embodiments include solarpanels that increase the acceptance angle without the need to move thepanel. In these embodiments, concentrators are used in variousarrangements so that a solar collection system need not rely on amechanical system for moving the panel or portions thereof as the sun'sposition changes. In other embodiments, a single-axis translational orrotational mechanical system may be used to increase the acceptanceangle. This is accomplished by either orientating the PV materialrelative to a lens, or using different lens types. Other embodimentsadopt a shifting method or place PV cells at different locationscorresponding to the focus point of a lens throughout the year. Alsodisclosed are methods and devices for increasing the performance at thePV cell level, again, without an increased need for relatively scarce PVmaterial, as the case may be; so that more electrical energy can bedrawn from an existing, finite or limited number of PV cells. Alsodisclosed are cost-effective approaches for deploying solar collectionsystems. According to this aspect of the invention, a more versatilesystem for arranging panels is provided that takes into accountdifferent environments for mounting panels which may be less than idealgiven the sun's position in the sky. The disclosure also includesdescriptions of solar collection devices that may be used in connectionwith, e.g., tracking, partial tracking or non-tracking panels, dependingon need.

According to another embodiment of the invention, a solar collectingtile includes a plurality of PV strips, a plurality of linearconcentrators, each concentrator positioned to concentrate solarradiation on a respective one of the plurality of PV strips, and whereinthe solar collecting tile has a perimeter that has four sides, more thanfour sides, or it is circular.

According to another embodiment of the invention, a solar panel kitincludes a first and second solar collecting tile, wherein each tile'ssolar-collection area is defined by a perimeter having four sides, orhaving more than four sides, or having a round perimeter. Each tileincludes a plurality of PV strips, a plurality of linear concentrators,each concentrator positioned to concentrate solar radiation on arespective one of the plurality of PV strips, and a connector forconnecting any side of the first tile to any side of the second tile.

According to another embodiment of the invention, a method for mountinga solar panel includes the steps of placing a frame on a structure, theframe having a plurality of panel mounts, locating an optimal panelorientation based on the sun's path, and arranging one or more panelshaving linear concentrators in the mounts among at least three differentangular positions depending on the located path of the sun.

According to another embodiment of the invention, a deployable solarpanel includes a plurality of linear solar-collecting elements, each ofwhich including a linear concentrator disposed over a PV strip such thatthe linear concentrator concentrates incident solar energy over a lengthof the PV strip, and a hinge interconnecting each of the linearsolar-collecting elements to an adjacent solar-collecting element. Insome embodiments, the linear concentrators are rod lenses.

According to another embodiment of the invention, a solar panel kitincludes a plurality of solar energy collecting strips, each of whichincluding a linear concentrator, a left and right hinge adapted forbeing engaged with other strips, and a PV strip located at the line offocus of the linear concentrator.

According to another embodiment of the invention, a method for deployinga deployable solar panel includes the steps of providing a panel in arolled-up form, wherein the panels includes a plurality of concentratorsconnected by hinges and each concentrator has at least one PV cellintegral to it such that the concentrator focuses reflected light ontothe PV material, unrolling the panel, and then connecting the PV cellsto each other to form a circuit.

According to another embodiment of the invention, a solar cell includesan upper, sun-facing side formed by a PV material and a currentconducting material, and a reflector arranged over the currentconducting material such that solar radiation directed towards thecurrent conducting material is reflected towards the PV material.

According to another embodiment of the invention, a solar collectiondevice includes a solar cell comprising a PV material and contacts forcollecting current from the PV material, the contacts being disposed ona sun-facing side of the solar cell, and a substrate, disposed over thesolar cell, having a plurality of notches formed thereon, wherein thesubstrate is arranged over the solar cell so that surfaces forming thenotches will reflected light away from the contacts and towards the PVmaterial.

According to another embodiment of the invention, a method ofmanufacture for a solar cell includes the steps of disposing a PVmaterial and plurality of metallic contacts on a substrate, forming aplurality of reflectors matching the locations of at least some of thecontacts, and disposing the reflectors over the at least some of thecontacts.

According to another embodiment, a solar cell includes a means forconcentrating light away from a current-carrying bus and towards PVmaterial. The means may include lenses that focus reflected light ontoPV material, refracted light onto PV material, or a combination of thetwo.

According to another embodiment, a solar cell includes conductors and PVmaterial, and a first and second lens operatively disposed in relationto the conductors and PV material, respectively, so that light isreflected and/or refracted away from the conductors and reflected and/orrefracted towards the PV material.

According to another embodiment of the invention, a static solar panelhas a first spatial frequency for a plurality of PV strips or PV cells,and a second spatial frequency for concentrators configured to focuslight on the cells or strips, wherein the spatial frequencies aredifferent from each other. The focused light can be refracted light, asin a lens, and/or reflected light, as in a minor. The cells or stripsmay be separated by a length L, and the concentrators, e.g., rods, maybe separated by a length M, and L is not equal to M. L can be such thatL<<M, or L may be slightly less than M or greater than M or L>>M. L maybe the same everywhere and/or M may be the same everywhere (equalspacing), such that the spacing may be described by a spatial frequencynumber.

The PV cells or strips may have a spatial frequency such that anintersection of this frequency with a spatial frequency for aconcentrator corresponds to a particular time of year or a particulartime of day in which at least one PV cell receives focused light and atleast one other PV cell does not receive focused light. Or the PV cellsmay have a first spatial frequency and a second spatial frequency suchthat an intersection of these two frequencies with a spatial frequencyfor a concentrator corresponds to both a particular time of year andparticular time of day in which at least one PV cell receives focusedlight and at least one other PV cell does not receive focused light.

According to yet another embodiment of the invention, a solar collectionunit includes a first and second concentrator, each having an axis ofsymmetry, a first PV cell arranged relative to the first concentratorsuch that the first PV cell captures focused light when a substantialamount of focused light is not substantially coincident with the firstaxis of symmetry, and a second PV cell arranged relative to a secondaxis of symmetry such that the second PV cell captures focused lightwhen a substantial amount of focused light is substantially coincidentwith the second axis of symmetry. The focused light can be eitherreflected or refracted light, or both reflected and refracted light. Thereflected light can be TIR light. The lens may be a parabolic lens,partially parabolic lens, a lens approximating a parabolic lens, orother suitable lens type. The PV cell or strip may be arranged atdifferent positions on a TIR plane (or above a TIR plane) correspondingto a different time of the day or time of the year, e.g., solstice,equinox, etc.

According to another embodiment of the invention, a static solarcollection system includes a first set of concentrators configured forfocusing solar energy onto PV material during a day of the year and/ortime of day, and a second set of concentrators configured for notfocusing solar energy onto PV material during the day of the year and/ortime of day. In this case, the concentrators may be 1-axis or 2-axisconcentrators (e.g., rod lens or spherical lens, respectively), thepanel may be static in both axes or only one of the axes, and theconcentrators may focus reflected, refracted or both refracted andreflected light onto PV material. The second set of concentrators areconfigured to focus light onto PV material during a different time ofthe day and/or year.

According to another embodiment of the invention, a static solar panelincludes a plurality of linear concentrators, e.g., rods, each having aline of focus dependant upon the angle of incidence of solar energyduring the course of the year, a plurality of PV strips, each of whichbeing arranged below a respective one of the concentrators, and asupport layer supporting the PV strips, wherein at least a portion ofthe support layer is configurable among a plurality of sun focusingpositions by linear displacement of the support layer.

According to another embodiment of the invention, an apparatus forcollecting solar energy throughout the year and of the type having allsolar energy collecting units lying within a common plane includes afirst collecting unit including concentrators having a line of focus,the concentrators being aligned with PV strips cells such that the lineof focus is substantially not coincident with the PV strips during afirst time or year, a second collecting unit including concentratorshaving a line of focus, the concentrators being aligned with PV stripscells such that the line of focus is substantially coincident with thePV strips during the first time of year. The first and second collectionunits may be separate, modular solar panels that are releasablyconnectable with each other to form a solar collection unit that isconfigured to focus light onto PV material at different times of theyear.

According to a method of configuring a solar collection unit a firstpanel configured to focus light onto PV material only during a firstportion of the calendar year is connected together with a second solarcollecting unit configured to focus light onto PV material only during asecond portion of the calendar year so as to create a solar collectionunit configured for focusing light onto PV material during both thefirst and second portions of the year. The first portion of the year mayinclude the equinox and the second portion of the year may include thesolstice.

According to another embodiment of the invention, a solar panel thatincreases the acceptance angle includes a first layer forming aplurality of linear concentrators, each of which having an axis ofsymmetry for a lens type, and a plurality of PV strips arranged in apattern such that a first PV strip is positioned to the left of the axisof symmetry, and a second PV strip is positioned to the right of theaxis of symmetry, wherein the solar panel is configured as fixedrelative to the earth.

According to another embodiment, a solar collecting unit capable ofincreasing an acceptance angle for PV material for a non-tracking panelincludes a plurality of concentrators, wherein the axes of symmetry oflenses are arranged relative to a plurality of PV strips/cells such thatno more than a portion of the PV strips/cells receive focused lightduring any time of the year.

According to other embodiments the acceptance angle of a solarcollection device may be increased in various ways. In one suchembodiment a solar collection device includes a concentrator having acollection area (meaning the area of the concentrated light on the PVmaterial) and PV material having an exposure area, wherein thecollection area is less than the exposure area.

According to another embodiment, a non-tracking solar collection systemincludes concentrators positioned relative to PV material such that atleast a portion of the light collected by the concentrators is directedat PV material, wherein the acceptance angle for the solar collectiondevice is such that the at least a portion of the collected lightdirected at PV material is approximately constant as the sun's apparentposition changes.

According to another embodiment of the invention, a sun position sensingelement for a solar panel includes a first end, a second end having atleast one photodiode disposed thereon, and means for detecting a changein the sun's apparent position.

According to another embodiment of the invention, a sun position sensingelement includes a photodiode having at least one active area, anaperture configured to receive sunlight, and a circuit for detecting theintensity of solar energy incident on the active area, wherein based onthe intensity of detected light a determination can be made as towhether the sun is in a first or second position.

According to another embodiment, there is a method for increasing theacceptance angle for a solar panel, the solar panel including aplurality of concentrators and corresponding PV material configured toreceive focused light from the concentrators. These methods include thestep of rotating each of the concentrators about their lens axes as thesun's apparent position in the sky changes.

According to other embodiments a solar collection device is translucent.When mounted to structure, the panel may be less noticeable to anobserver. In one example, a panel having linear concentrators with PVmaterial attached to the concentrators is suspended from a frame.According to these embodiments, a solar panel can blend into thestructure to which it is mounted, e.g., a rooftop. In other embodiments,the panel includes include patterns, messages, and/or colors. In oneexample, each rod lens includes a pattern or portion of a pattern overthe unused part of the lens material, i.e., the portion of the lens notfocusing solar energy.

According to other embodiments a solar collection device, having acollection plane, is configured to rotate about an axis normal to thecollection plane when the sun's apparent position in the sky changes. Inone example, the panel includes an array of linear concentrators, suchas an array of rod lenses. Each rod lens may have PV material secured toit, or located relative to the lens, so that focused light is receivedon the PV material as the panel is rotated to follow the sun.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B depict two perspective views of a photovoltaic (PV) cellfor converting solar energy into a electrical energy

FIG. 2 depicts a cross-sectional view of a PV cell.

FIG. 3A depicts a cross-sectional view of PV cell having a transparentlayer for reflecting solar energy towards PV material.

FIGS. 3B-D depict alternative embodiments of transparent layers forreflecting and/or refracting light towards PV material, including insome embodiments the use of cut-outs, grooves or surfaces intended toreflect light.

FIG. 4 depicts a cross-sectional view of PV cell having reflectingstrips positioned over electrical contacts.

FIGS. 5A-5B depict perspective and cross-sectional views of embodimentsof a solar panel or module incorporating linear concentrator elementsthat focus refracted light onto PV material.

FIGS. 6A-6B depict perspective and cross-sectional views of embodimentsof a solar panel or module incorporating linear concentrator elementsthat focus reflected light onto PV material. This example shows apartial parabolic lens. However, the same concept is readily adapted foruse with other lens types, including lenses that only approximate a lenstype or lenses that do not correspond to a standard lens type but arenonetheless capable of focusing reflected light onto PV material.

FIG. 7 depicts the orientation of a solar panel having a panel axis andlinear concentrators according to FIG. 5 or 6 relative to the eclipticplane. Unless otherwise noted, whenever a discussion refers to thedirection of reflected light relative to PV material for a panel thatincludes linear concentrators and the orientation of the panel is notspecified or otherwise apparent based on the discussion, the discussionassumes that a panel axis is fixed relative to the Earth and extends inan East-West direction, and the panel faces towards celestial equator.

FIGS. 8A-8C depict embodiments of a sun position sensing unit that maybe used on a tracking platform to track a solar panel or guide a user tolocating a position corresponding to maximum solar flux.

FIGS. 9A, 9B, 10A and 10B depict embodiments of static solar collectiondevices that are capable of increasing the acceptance angle at theexpense of increasing exposure area.

FIGS. 11 and 12 depict embodiments of a single-axis dynamic solarcollection device capable of increasing an acceptance angle.

FIGS. 13A-13B depict two perspective views of a hexagonal solarcollecting module.

FIGS. 14A-14B depict top views of a solar panel, or solar collectingunit assembled from hexagonal solar modules according to the embodimentof FIGS. 13A-13B.

FIGS. 15A-15C depict aspects of embodiments of a portable or roll-upsolar panel.

FIGS. 16A-D depict additional embodiments of a solar collection devicethat use linear circular cross section concentrators with the PVmaterials directly attached to them and are capable of rotating inunison.

FIGS. 17A-B depict perspective and frontal views of a solar panelaccording to another aspect of the disclosure. This solar panel isconstructed to dynamically follow the sun and includes a translucentconstruction and sweeping/cleaning portions that are integrated into thesupport frame for the panel.

FIGS. 18A-18D depict solar panels according to another aspect of thedisclosure. The solar panels include one or more patterns formed onunused portions of a concentrator for the purpose of creating a pattern,image, etc. to persons viewing the panel. FIG. 18A shows a frontal viewof a concentrator suitable for the solar panel depicted in FIG. 17A,which includes one or more patterns formed on sides adjacent the PVmaterial. A perspective view of this concentrator is depicted in FIG.18B. FIGS. 18C, 18D depict a solar panel that includes more than onepattern. At different times of the day a different pattern becomesvisible to person viewing the panel.

FIG. 19 depicts a perspective view of a solar panel that is mounted ordisposed over a window. The panel may be constructed in a similar manneras described in connection with the embodiments of FIGS. 16 and 17. Thesolar panel may form a curtain over a window. The curtain may beconfigured to allow diffused light to pass through while collectingdirect sunlight on PV material. In a related embodiment, the solar panelcan also be hung as a curtain over a window where the curtain also doesnot allow diffused light to pass through. In this case, the curtain mayfunction similar to a Venetian blind. It could also be integrated insidea window

FIG. 20 shows perspective view of a solar collecting element including acircular rod lens with attached PV strip.

FIGS. 21A-21B show portions of the solar collecting element of FIG. 20according to embodiments with and without additional concentrators,e.g., reflecting elements, positioned adjacent a metal grid forconducting current. The concentrators may be incorporated into the solarcollecting element in accordance with one or more of the embodimentsdiscussed in connection with FIGS. 3-4.

FIG. 21C depicts another embodiment of a solar collecting elementincluding a circular rod lens with attached PV strip. According to theseembodiments, a groove may be formed in the lens. The metal grid andconcentrators may then be attached within the groove, e.g., with asuitable adhesive.

FIGS. 22A-22D show ray traces for various embodiments of a solarcollection device.

FIG. 23 depicts an example of a static solar collection deviceconstructed in accordance with the principles discussed in connectionwith FIGS. 9A-9B.

FIG. 24A depicts one embodiment of a linear concentrator having unused(not focusing light) portions of the lens removed.

FIG. 24B depicts one embodiment of a linear concentrator in which thesides of a lens, e.g., a cylindrical rod lens, are shaped to reflectsolar energy towards a thinner strip of PV material. In this example, arod lens having a circular cross section has its sides partially removedto produce straight, tapered walls extending from a convex outer surfaceportion to the PV material. The tapered walls may be formed so as toproduce TIR, thereby increasing the concentration ratio for theconcentrator.

FIGS. 25A-25B depict a solar collection device, and a group of solarcollection devices utilizing rod lenses and a circular perimeter. Insome embodiments, the solar collection device is rotated about an axisnormal to the collection plane when following the sun's apparent motion.

DETAILED DESCRIPTION OF THE INVENTION

Photovoltaic (PV) solar cell efficiency, i.e., the percentage orfraction of the sun's energy striking the surface of a PV cell that isconverted into electrical energy, can range from about 5% to about 40%at present time. The supply of PV material, however, is not sufficientto meet demands at this time. This is particularly true for higherquality PV material such as crystal silicon or gallium arsenide. Thedisclosure provides several embodiments of solar collection devicesintended to increase the amount of power that can be drawn from PVmaterial, decrease costs of manufacture for solar panels, solar cellsthat can produce greater power output without increased demand on PVmaterial, and simplify the deployment of solar cells/modules/panels oralignment of such systems to make the best use of the sun's energy.

FIG. 2 depicts a cross-sectional view of the solar cell 1 depicted inFIGS. 1A-1B in more detail. The solar cell 1 has a sun facing side 2formed by an upper surface of the PV material layer 6 and the contacts 5a/ 5 b for collecting current, which are typically a metal or metalalloy. Below the PV material layer is a bottom electrode 7 forcollecting the opposite charge. The PV material and upper and lowerelectrodes may be supported on a substrate 8. As shown, light rays R1,R2 striking the sun-facing side 2 are absorbed, scattered and/orreflected by both the PV material 6 and the conducting material, i.e.,contacts 5 a/ 5 b. Any light that strikes the contacts 5 a, 5 b is notconverted into electrical energy and therefore is wasted. Typically, thepercentage of the sun-facing surface of a solar cell 1 taken by metalcontacts is between 10% to 20% of the total surface area.

A. Concentrating Solar Energy Onto the PV Material

It would be desirable to increase the percentage of the sun-facing side2 occupied by the PV material 6 so that a greater percentage of thesolar energy is absorbed by the PV material. However, if the width ofthe contacts 5 a/ 5 b, or number of contacts is reduced, then theresistance or loss in the circuit goes up. Resistance to the flow ofcurrent through contacts 5 a/ 5 b is inversely proportional to thecross-sectional area of the metal contacts and/or number of contactsover the cell. Thus, while it might seem desirable to simply removecurrent-conducting material, if the current pathways are too few, orreduced too much in size, then the lack of current conducting materialcan inhibit the flow of current.

FIG. 3A is a cross-sectional view of one example of a solar cell 20. Thecell 20 has PV material including a p-n or p-i-n structure as before, abottom electrode 7, and a substrate 8 supporting the cell 20. Inaddition, the solar cell 20 has a transparent film, layer or substrate22 (hereinafter “film 22”), which can be made from a glass, plastic orother material having a relatively low absorption coefficient. The film22 has formed on its lower surface 23 b a series of notches or grooves24 that cause light (as depicted by ray R1) to reflect away from thecontacts 5 a, 5 b and towards the PV material (R1′). The layer 22 has athickness “t”. In other embodiments, the film 22 may include a series oflenses centered between contacts 5, concave lens types over the contactsand/or convex lenses positioned over the PV material between contacts 5.The lenses may be arranged so that solar energy is concentrated usingreflected light or refracted light. In some embodiments, the film 22depicted in FIG. 3A may be arranged to create a condition of TotalInternal Reflection (“TIR”) onto the PV surface 6 a (as described ingreater detail, below). A light refracting concentrator may also be usedin combination with a concentrator configured to create a condition ofTIR.

In FIG. 3B light is concentrated onto the PV material using a series ofconvex lens elements 23 a triangular-type reflecting surfaces may beincluded (as shown) with the convex lenses. When these reflectivesurfaces (straight or curved) are included with the convex lenses, thenthe transparent film may be regarded as both a concentrator of reflectedlight and refracted light onto the PV material. As depicted, a light rayR1 is first refracted (R1′) then reflected (R1″) towards the PVmaterial.

In FIG. 3C, film 22 is formed as a series of convex lens elements onopposing surfaces 23 a/ 23 b. According to these embodiments, refractedlight is concentrated onto the PV material, by one convex surface 23 bor two convex surfaces (as illustrated). In some embodiments, fresnellenses or concentrators may be used instead. According to someembodiments, a reflective surface disposed over the contacts 5, e.g.,triangular-type elements, is used in combination with the double convexlens.

In FIG. 3D film 22 may be formed as an undulating or sinusoidal-typeseries of convex/concave lens elements 23 a. The concave lens (placedover a contact 5) diverts light away from a contact 5 while the convexlens (placed over the PV material 6 a) focuses light on the PV material.As depicted, triangular light-reflecting may also be formed so that acombination of reflected and refracted light is focused onto PV material(as before). In other embodiments, there is only the undulating orconvex-concave-convex type surface. In other embodiments, two surfacesmay have this pattern of convex-concave surface (i.e., same as FIG. 3Cexcept convex-concave-convex type upper and lower surfaces).

In some embodiments the lens element disposed over the PV material, thecontacts, or both may be a one-dimensional (1-D) concentrator, e.g., acylindrical lens element, or a two-dimensional (2-D) concentrator, e.g.,spherical lens element. The choice for the concentrator may also dependon the current conducting bus architecture.

The embodiment depicted in FIG. 3A will now be described in greaterdetail. It will be understood that certain aspects of the followingdiscussion also apply to the above aforementioned embodiments and thusfurther clarification is not necessary. The film lower surface 23 b maybe bonded to the PV material using an index-matching glue. The grooves24, preferably V-shaped, align over the contacts 5 a/ 5 b as shown. Thegrooves 24 may have a constant cross-section in the direction normal tothe FIG. 3A cross-section, and extend lengthwise over the film 22 sothat the contacts 5 a/ 5 b are enclosed within the grooves 24 over theirentire length. Referring to groove 24 b, for example, preferably thesides 25 a, 25 b forming this groove are straight and diverge from eachother as they extend towards surface 23 b. The space formed by the sides25 b, 25 a and the PV material surface 6 a (excluding the contacts 5 a/5 b) may be described by a triangle over the length of the contact 5 a/5 b. The grooves 24 may be formed by surfaces that are straight orcurved. The grooves may be identical to each-other or they may differfrom contact to contact. Some or all of the contacts may be placedwithin grooves.

The width at the base of the triangle depicted in FIG. 3A is about thewidth of the contact 5 a/ 5 b. The height of the groove 24 b (i.e.,distance from the base to apex of the triangle) may be chosen to createTIR such that substantially all of the light ray R1 reflects when itreaches the sloped surfaces, i.e., R1′. That is, there is no refraction,only reflection when light ray R1 reaches surface 25 a or 25 b. Thedepth and width of the groove 24 sufficient to provide TIR withoutshielding light from PV material may be computed from the width of thecontacts 5 a, 5 b. Further, as made apparent from the above description,the film 22 may use these triangular-type reflective elements (orparabolic type lenses) in combination with convex, concave or acombination of the two (see e.g., FIGS. 3B-3D).

In some embodiments, one or more grooves 24 may be coated with areflective material, such as by applying reflective paint to the grooves24 or by a deposition process. Depositing or applying a reflectivematerial may be desirable to account for situations when the cell 20 isnot faced directly towards the sun. In some embodiments, the top surface23 a may be formed with linear convex surfaces, e.g., as depicted byconvex surface 23 c, which can focus light more towards the PV materialbetween the contacts 5 a, 5 b.

Thus, according to this embodiment there can be an increase in solarflux striking the PV material as a result of both R1′ and R2 (i.e.,direct and reflected light) striking the PV material. An additionaladvantage of this arrangement is that the resistance in the circuitformed by contacts 5 a may be decreased because there is less radiationheating of the contacts 5. Since the surfaces 25 a, 25 b reflect some,if not all light directed towards contacts 5 the temperature of thecontacts 5 may be reduced which can reduce the resistance to currentflow in the metallic material. In some embodiments, however, thisdifference may be negligible since most heating tends to occur fromconduction, not radiation.

Referring to FIG. 4, in alternative embodiments a solar cell 30 hasreflecting strips 34 disposed over the contacts 5. The strips 34 may bebonded to, soldered to, or deposited on the contacts 5. The sides 35 a,35 b of the triangular-like strip reflect light ray R1 towards the PVmaterial. Thus, according to this embodiment there is also an increasein solar flux striking the PV material as a result of both R1′ and R2(i.e., direct and reflected light) striking the PV material.Importantly, the increase need not come at the expense of removingconducting material from the surface 6. The strips may be formed overthe contacts by masking techniques. They may be formed over pre-made PVcells having contacts or formed integral with the contacts, e.g.,forming upper surfaces that are pointed (e.g., triangular incross-section, straight over the length).

In some embodiments strips (FIG. 4), films or lenses (FIG. 3) may bemanufactured with relatively high optical tolerances. In otherembodiments, a relatively low cost and imprecise surface topology mayyield significant, desirable, and/or sufficient increases in solar fluxdirected to the PV material. For example, as depicted in FIG. 3triangular grooves are formed in a transparent sheet of material that isthen placed over the contacts 5, as opposed to forming, e.g., paraboliclenses in the film 22. The slopes 25 b may therefore be straight (asshown), or more precisely curved depending on the particularapplication.

In some embodiments a groove or triangular strip may be formed over oneor both current collecting 5 a and bus 5 b contacts (see e.g., FIG. 1A).With respect to the triangular strips 34 embodiments, the bus contact 5b, or both the bus and current collecting contacts 5 a, 5 b may beformed to have a triangular upper surface. In these cases, there may bebenefits in reduced resistance in the circuit (since resistance isinversely proportional to cross-sectional area) without the possibleconcern of whether PV material becomes shielded from light energy by theraised surfaces of the contacts.

It will be appreciated that one or more of solar cells 20 and 30 may beincorporated into the following embodiments of a solar module or panel,which are additional aspects of this disclosure. For example, theprinciples set forth above may be incorporated into a preferredembodiment that uses rod lenses, as discussed in connection with FIGS.17,19 and 22-24. The foregoing embodiments and the following additionalembodiments therefore should be understood as not mutually exclusive ofeach other. Rather, one of ordinary skill will appreciate how theembodiments may be combined based on the teaching of Applicants'disclosure, and selected based on particular power needs, environments,available space, resources, budgets, etc. in view of this disclosure.

FIGS. 5A and 5B depict a partial perspective view of one embodiment, anda partial cross-sectional view of another embodiment of a solar panel50. Solar panel 50 may be configured to increase an acceptance anglealong the off-axis (e.g., perpendicular to the panel axis). The solarpanels of FIGS. 5A and 5B include a plurality of strips 11 containing PVmaterial mounted on a supporting substrate 18. The strips 11 may includea single, elongated cell or several smaller cells aligned along a panelaxis (FIG. 5A) and electrically connected to each directly or via acentral bus. The cells aligned together along the panel axis may beconnected in parallel or in series. For example, the negative electrodesof cells forming the PV strip 11 may be connected to a central bus onone side of the PV strip 11, and the positive, lower electrode may beconnected to a central bus located on the opposite side of the PV strip11.

The embodiment depicted in FIG. 5A includes a linear concentrator layer53 having cylindrical, converging lenses 54 centered over each strip 11.In the embodiment depicted in FIG. 5B, the cylindrical lenses arereplaced with a linear concentrator layer 52 having Fresnel lensescentered over the PV strips 11. In each embodiment, the lenses may belocated over the PV strips 11 and spaced appropriately so that solarenergy is focused over only the width of, and over the entire length ofthe strips 11. The strips 11 may also be directly attached to lenses (asdiscussed below). The lenses 52/53 may be formed from any suitablematerial having a relatively low absorption coefficient. As shown, thesolar flux over the length of each PV strip 11 comes from focused,refracted light R1′, R2′. The top surface 53 a, 52 a may be convex ineither embodiment (i.e., similar to layer 22 in FIG. 3C). The surfaces18 a of the substrate may have a metallic layer, or the substrate may bein-part formed from a metal so that it can serve as a heat sink.Alternatively, radiating heat fins may depend from the lower surface ofsubstrate 18 to dissipate heat. A heat pipe may also be provided in thesubstrate 18 to increase heat transfer. In case of direct attachment tothe lenses (as discussed in greater detail, below), the lens itselfcould be part of the heat dissipating medium.

In an alternative embodiment the PV strips 11 may be positioned toreceive reflected, as opposed to refracted light. For example, asdepicted in FIGS. 6A-6B PV strips 11 are configured relative to a lenshaving features of a linear parabolic lenses so that solar energyfocused on the PV strips 11 is concentrated using reflected light. Thus,light rays R1 and R2 are reflected onto the PV strip 11 as rays R1′ andR2′, respectively, by each of the respective parabolic, linearconcentrators 62. The top surface of the lens 62 may be flat (as shown)or may have a linear convex lens section centered over each paraboliclens 62 a (i.e., similar to layer 22 of FIG. 3B). Although a lens havingfeatures of a parabolic is depicted in FIGS. 6A-6B and accompanyingFIGS. 7A-7B, below, it will be understood that the same principles arereadily applicable to other lens types, including standard type lens ora general lens type capable of focusing reflected light onto PV materialin accordance with this disclosure.

The foregoing embodiments of panels 50 and 60 refer to linear or 1-Dconcentrators. FIG. 7 depicts the position of panel 50 (refracted light)or panel 60 (TIR or reflected light) relative to an apparentlongitudinal path of the sun during the course of a day. As shown, thearrow indicating a “panel axis” may extend parallel to the lens axis fora linear concentrator. For example, a panel axis is shown relative tothe PV strips 11 and line of focus for the linear concentrators 53 inFIG. 5A.

B. Tracking Panels Or A Portion Thereof

Panels 50/60 may be tracked about a single axis or two axes using anyknown mechanism for rotating a solar panel so that the PV strips remainpointed directly at the sun throughout the day. For example, panels50/60 may be tracked using the mechanisms disclosed in U.S.2004/0246596. Referring to FIG. 8A, panels 50/60 may be mounted to asingle or bi-axis mount 72 configured for tracking longitudinal and/orlatitudinal changes in the sun's position. The mount 72 may have asingle or double gearing mechanism well known in the art for trackingthe sun motion remotely, automatically or manually based on an input setof coordinates. The mechanism may be configured to rotate the panelthrough a continuous range of angles, or through discrete angularpositions, e.g., 10, 20, 30, etc. degrees. To track the sun's positionduring the day, the mechanism 72 has a gearing or actuator (e.g.,hydraulic, magnetic, or manually actuated) for rotating the panel 50/60about axis “Y” depicted in FIG. 8A (longitudinal adjustments). Forlatitudinal adjustments, the mechanism, gearing or actuator (e.g.,hydraulic, magnetic, or manually actuated) can rotate the panel 50/60about axis X. Any assembly and control system known in the art forsingle or two-axis rotation of a solar panel based may be used tore-position panel 50/60.

In some embodiments, a panel 50/60 has only a mechanism, gearing oractuator for translation of a substrate holding, supporting or includingPV material relative to concentrator lenses as the sun changes positionabove the horizon, as described in greater detail below. For thisembodiment, it may only be necessary to translate the PV strips 11relative to the lenses, i.e., lenses 52, 53, as the latitudinal positionof the sun changes, since the linear concentrators can collect asignificant amount of the sun's energy over the course of the daywithout adjustment in the longitudinal direction (e.g., rotation aboutthe “Y” axis in FIG. 8A).

In some embodiments, a sun position sensing element 70 is used todetermine which way to rotate (and/or translate) the panel 50/60 so thatthe most direct sunlight is received on the PV strips 11 at any timeduring the day and/or over the course of the year. The position sensingelement 70 may be rigidly mounted to the panel 50/60 (i.e., so that theposition sensing element 70 moves with the panel), or the positionsensing element 70 may be moved separately from the panel 50/60, inwhich case angular adjustments in the position sensing element 70 arecommunicated to the actuator or mechanism for making similar adjustmentsin the panel 50/60. Preferably, a position sensing element 70 is basedon the relative intensities of solar energy detected by active areas ofone or more photodiodes. For example, a position sensing element 70 maybe made using one or more of the SPOT Series Segmented Photodiodesoffered by OSI Optoelectronics (downloaded from<http://www.osioptoelectronics.com/product detail.asp?id=20&series-=Quadrant+% 2F+Bi%2Dcell+Photodiodes> on Feb. 6, 2008).Such an approach for sun tracking is very low cost effective and offersa reliable and accurate method for tracking the sun's position in thesky. The position sensing element 70 uses one or more photodiodes'active areas to determine when the panel is no longer pointed directlyat the sun based on the difference or change in/between/among the signalstrength in active area(s) (note: the sun position sensing element 70depicted in FIG. 8A is not drawn to its actual scale relative to thepanel 50/60).

A sun position sensing element 70 may have a photodiode with four (ormore) active areas and as few as two active areas for sensing the sun'sposition. FIGS. 8B and 8C depict two such embodiments. Each sun positionsensing element 70 may have a cylindrical casing 74, an entrance end72/73 and an image or detection plane 75. The embodiments depicted inFIGS. 8B and 8C have a converging lens 72 located at the entrance end.Alternatively, the lens may be replaced by an opaque cover having asmall opening.

The embodiment of 8B has a photodiode with four active areas, 76 a, 76b, 76 c, and 76 d arranged about a central point and defining quadrantsI, II, III, IV as shown. According to this embodiment, the positionsensing element 70 can detect longitudinal and latitudinal changes inthe sun's position relative to the panel 50/60. For example, assume thatlongitudinal motion of the sun corresponds to movement parallel to theY-axis direction and latitudinal movement corresponds to movementparallel to the X-axis direction (see FIG. 8A). If the sun moveslongitudinally, then the focus point will move from the center point(where the signal intensity is about the same among all active areas 76a, 76 b, 76 c and 76 d) to a location where most of the focused image islocated in quadrants I and 11. When this occurs, the circuitry willdetect a difference in at least one of the pairs of signals beingreceived from the diodes occupying quadrants I and 11 verses quadrantsIII and IV. Similarly, if the sun moves in the latitudinal direction(-X), then the signal received from the diodes in quadrants I and IVwill increase over the signals received from quadrants II and III.Therefore, for the hybrid movement of the sun depicted in FIG. 8B, thesignal received from quadrant II will be greater than the signalsreceived from quadrants I, III and IV. Based on a comparison (e.g.,difference) of signals, a processor may send a command signal to rotatethe panel 50/60 about the X and Y axes until the signals received fromactive areas 76 a, 76 b, 76 c, and 76 d are approximately of equalintensity (i.e., the focused image is once again centrally located). Thedetection plane in the embodiment of FIG. 8C has only two active areas76 a, 76 b. For this embodiment, the position sensing element 70 detectsonly apparent longitudinal or latitudinal motion of the sun based on achange in the signal received between diode 76 a (quadrant I) and diode76 b (quadrant II).

C. Static Panels Or Solar Collection Devices

In some embodiments, the costs and complexities of a tracking system forthe panel 50/60 may be too much, not possible or simply not worth theeffort for a given application; for example, if panel 50/60 is used as aroofing tile or otherwise formed as a layer of a building wall, orotherwise when a more simplified and cost-effective solution is neededfor a year-round solar energy source. Tracking systems can becumbersome, require maintenance, and may be difficult to maintain inclimates with extreme weather changes. Additionally, the available spacefor mounting a panel may not be a design constraint. As such, it may bethe case that a design need not concern itself with optimizing theefficiency of a panel when efficiency is being measured in terms of thetotal surface area occupied by the panel in relation to the poweroutput. Rather, the design may prefer non-moving parts while providing apanel that focuses light onto PV material throughout the year, even atthe expense of lowering the panel's efficiency.

The following discussion describes embodiments of solar panels capableof providing 1D and 2D increases in an acceptance angle. The embodimentsinclude panels with and without moving parts. Examples of the latertype, i.e., static panels, will be discussed first.

In some embodiments, a static solar collection device may correspond todisposing reflective material on the surfaces of a concentrator intendedfor concentrating reflected light onto PV material, such as in theembodiment depicted in FIGS. 6A-6B (reflective material may be disposedon surfaces 62 a, 62 b, 64 a, 64 b). In other embodiments, the PV stripposition may be positioned at different locations relative to a lensaxis of symmetry. In the embodiments of the solar collection devicesdepicted in FIGS. 5-6 all of the PV strips are located at an axis ofsymmetry for the lens type. This arrangement may be thought of as asolar collection device in which the spatial frequencies of the PVstrips are matched with or identical to the spatial frequencies of thelenses. When the spatial frequencies are matched in this manner then allof the PV strips receive focused light at the same time. In a differentsense, the PV strips collect focused light when the focused light issubstantially centered at the axis of symmetry. Thus, in the embodimentsof FIGS. 5-6 when the sun is directly overhead, all PV strips receivefocused light. However, unless the panel is tracked, or the lenses andPV strips are moved relative to each other, then all PV strips will alsonot receive focused light when the sun has changed position, e.g., incase of a East-West oriented panel, from the equinox to the solstice. Inthe case where the PV material and lens are matched such that theentirety of the focused light strikes PV material, but any change inposition of the sun causes a portion of the focused light to no longerstrike PV material, the solar panel may be said to have an acceptanceangle. This acceptance angle may be increased in one of two ways, bytracking the panel (in which case the acceptance angle may no longer ofimportance since the panel may always face directly at the sun) or byincreasing the amount or location of PV material relative to lenses.

Referring now to FIGS. 9A, 9B, 10A and 10B according to some embodimentsthe spatial frequencies of PV strips/cells (distance between adjacentstrips/cells located on a substrate) are not the same as spatialfrequencies of the concentrators (distance between adjacent lens axes).Thus the value for “M” depicted in FIGS. 9A and 9B is not equal to “L”.This construction allows a solar collection device to provide the sameamount of focused light onto PV material throughout the year, withoutthe need for moving or adjusting the relative position of the lenses andPV material. That is, no portion of the panel need to be moved as thesun changes its apparent position in the sky. This and other advantagesof static panels, to be described below, apply equally to collectiondevices that use 1-D or 2-D concentrators.

PV strips 11, 12, 13 and 14 in FIG. 9A depict different positions of PVstrips/cells relative to a nearby axis of symmetry for a lens (referredto as a “lens axis” in the drawings). Alternatively, these strips mayindicate the different locations of a focus point for concentrators overthe course of a year. These PV strips will be relied on as an example toillustrate embodiments of a static collection device. In this example,axes of symmetry for each lens may be parallel to each other. Strip 11is located to the right of this axis and does not receive focused lightwhen the sun is directly overhead (R1′, R2′). However, PV strip 14,which is centered on the axis, would receive this focused light. Whenthe sun has changed position (light rays R3, R4) a PV strip 12, whichlike PV strip 11 is to the right of an axis of symmetry, receivesfocused light whereas PV strip 14 (centered) and a PV strip 13 (to theleft of an axis of symmetry) would not. Similarly, when the sun'sposition is such as represented by rays R5 and R6, PV strip 13 wouldreceive focused light whereas PV strips 12,14 and 11 would not receivefocused light. A solar collection device having concentrators positionedrelative to PV strips in a manner consistent to the foregoingdescription may provide a static panel feature. That is, a panel'sacceptance angle can be effectively increased to follow the sun'sapparent motion without itself being moved. For example, suppose thesolar collection device depicted in FIG. 9A was located at the equator.During the equinox, assuming the apparent motion of the sun on equatorand at equinox is solely along the panel axis (see FIG. 7), PV strip 14would receive more solar energy than PV strips 11, 12 or 13, whereasmore solar energy would be received by strips like 11, 12 and 13 than PVstrip 14 during the winter solstice and summer solstice periods. Thus, arelatively constant amount of light may be focused onto PV stripsthroughout the year without having to physically track the panel or movea lens relative to PV material so as to follow the sun. One particularimplementation of the panels described in FIG. 9A-9B is shown in FIG.23.

The foregoing example referred to a collection device that includedlinear or 1-D concentrators. In other embodiments a collection devicehaving 2-D collectors may have a 2-D capability for increasing anacceptance angle. As such, the foregoing discussion and the discussionthat follows will be understood to apply equally to collection devicesthat include PV strips (1-D concentrator used) or PV cells (2-Dconcentrator used). In the 2-D case there may be a capability toincrease the acceptance angle in one or two axes, e.g., along two axesthat are perpendicular to each other.

As mentioned above, in some embodiments a static device may be describedby a lens spatial period (“M”), and a PV strip/cell spatial period(“L”). Assuming the panel axis is along the East-West direction and thepanel is directed and fixed at the celestial equator in the sky, becauseL is not equal to M some PV strips receive focused light at a certaintime of year whereas others do not. This concept is depicted graphicallyin FIGS. 10A and 10B. FIG. 10A depicts a top view of static panel 80that uses 2-D concentrators, and FIG. 10B depicts a top view of a staticpanel 80 that uses 1-D concentrators. In FIG. 10A there are shown 81spherical lens elements and in FIG. 10B there are nine cylindrical lenselements. The clear, single hatched and cross-hatched lines, a solid,respectively, indicate the periods during the year when a PV strip orcell is or is not receiving focused light. For example, referring to thecase of FIG. 10B at the autumn or spring equinox a PV strip is receivingfocused light from a lens element 54 c, a PV strip is receiving focusedlight from a lens element 54 b (single hatching) at the winter solsticeand a PV strip receives focused light at the summer solstice from a lenselement 54 a (cross-hatching). In contrast, for the same spatial periods(L=M) and size PV strips all or none of the lens elements in FIG. 10Bmay focus light on a PV strip at a certain time of year, and/or time ofday. However, since L is not equal to M, the PV strips receiving focusedlight may be selectively varied over the course of the year or day. Assuch, a relatively constant amount of focused light is directed towardsPV material without a need to move lenses relative to PV material, or toactively track a panel. In the case of 2D concentrators (FIG. 10A)during a certain time of the day some of the PV material is receivingcollected light (clear circles 54 d) whereas others (solid circles 54 e)are not. As the sun's apparent position in the sky changes, so do thelenses that direct focused light onto PV material.

As alluded to above, the solar collection device may increase theacceptance angle, statically in one axis, while the device is rotatedabout a second axis, i.e., the device may be both a static anddynamically device. In other embodiments the device is static in bothdirections by selecting a spatial frequency of PV cells in the “Y”direction (e.g., longitudinal apparent motion of the sun) and a spatialfrequency of PV cells in the “X” direction (e.g., latitudinal apparentmotion of the sun). These PV cell frequencies may be the same ordifferent from each other. However, both are different from therespective X and Y spatial frequencies for the 2-D lenses (if sphericallens elements are used then the X and Y frequencies may be the same).Thus in similar fashion, different PV cells would receive focused lightduring the day, and those PV cells receiving focused light during acertain time of day during, e.g., the solstice period, would not receivefocused light during the same time of day during the equinox. However,regardless of the time of day when the sun is in the sky, or the time ofyear, the solar collection device's PV cell/strip vs. lens spatialfrequencies can be selected so that approximately the same amount offocused light is being received on PV material at any time when solarenergy is available for collection.

In some embodiments, a method of designing or assembling a statictracking panel may be geared to arriving at a desired intersection ofthe spatial frequencies. For example, the patterns depicted in FIGS. 10Aand 10B are, according to some embodiments, repeating and may beconsidered as a spatial frequency derived from the intersection oroverlapping areas of the spatial frequencies. Thus, the number of PVstrips/cells receiving focused light throughout the year/day may be thesame as this third spatial frequency remains constant but their locationshifts (e.g., clear to single hatch concentrators in FIGS. 10A-10B is ashift due to a change in the sun's apparent position from equinox tosolstice) as the sun's apparent position over the day/year changes.Again, essentially the same number or percentage of the PV material maybe receiving focused light throughout the year, although differentstrips/cells are being used to generate solar power for different timesduring the year and/or day.

In the foregoing examples of a static device the spacing or location ofPV strips (or cells) relative to an axis of symmetry (see FIG. 9A) maybe defined by a spatial frequency value. In other embodiments a staticdevice may instead be defined by the distance of PV strips or cells fromthis axis. For example, in the embodiment depicted in FIG. 9B a staticdevice utilizes reflected light, as opposed to refracted light. Sincesome portion of a PV strip or cell located between the concentrators (inthis case parabolic concentrators) would never receive a significantamount of reflected light, it may be preferred to construct the staticdevice by identifying a series of PV strip/cell positions relative to anaxis of symmetry and then placing the PV strips at various positionswithin that length (e.g., a 1-D concentrator), or within that radius(e.g., 2-D spherical concentrator/two axis). Thus, as depicted in FIG.9B the static device may have ⅓ of the PV strips (13) located to theleft of an axis of symmetry, ⅓ are located at the center (14) and theremaining third are located to the right of an axis of symmetry (12). Inother embodiments, more of the PV material may be located at, e.g., thesolstice positions than at the equinox positions (although a lens havingfeatures of a parabolic lens are depicted in FIG. 9B, the principle isreadily applied to other lens types capable of providing focused lightonto PV material in view of the foregoing disclosure).

D. Dynamic Panels Or Solar Collection Devices

Referring to FIGS. 11 and 12, according to another aspect of thedisclosure PV material or lenses are moved relative to each other toincrease an acceptance angle (dynamic solar collection devices). Forpurposes of describing this embodiment, reference will be made toembodiments that use refracted light concentrated using fresnel-typelenses. According to these embodiments, the PV strip supporting layer orsubstrate 18 may be translated relative to the lens layer 52 (fromposition 18 to position 18′) so that PV strip 11 can be moved toposition 11′. Thus, the PV strips 11 a/ 11 b may be moved from positions11 a, 11 b to 11 a′, 11 b′ relative to lenses 52 a, 52 b, respectively.FIG. 12 depicts a cross-sectional side view of a portion of a solarmodule or solar panel depicting schematically an arrangement of thepower collection connections and inter-module connection. Thearrangement for collecting power at the module level, interconnectionfor collecting current and transfer to a central bus, DC to ACconversion, circuit-breakers when power is shared, etc. (as discussedearlier) may be easily implemented by one of ordinary skill based on theforegoing description, e.g., as implemented in U.S. Pub. No.2003/0111103. Solar panel 90 may include a lower frame portion 94, sideframe portion 96, an electrical connection 97, wiring among the PVstrips in the panel 90, and a movable substrate or platform 92 for thePV strips so that they may be re-positioned relative to lens elements ofthe lens cover or layer 52.

Lower frame portion 94 may have a heat dissipation side 94 b that mayinclude fins, heat pipes, or a vent for recirculation of air through theinterior space of the panel. The upper portion 94 a of the lower frameportion 94 may have a groove that receives a tongue or rail portion ofthe substrate or PV strip platform 92 so that the platform 92 can beslid over the frame 94. The platform 92 may be slid manually or by amotor when the PV strips are adjusted relative to the lens 52 in orderto maximize solar flux as the seasons change. The panel may include asun position sensing element that can be used to control the position ofthe platform, or the tracker may be used as a guide to locate the bestposition of the platform 92 when there is a manual adjustment made.

The metal connection 97 allows panel 90 to be electrically connected toan adjacent panel having a complimentary connection. Connection 97 onone side may be designated as the positive (+), and the opposing sidenegative (−) so that panels may be placed in series like batteries.Alternatively, the connection 97 may have both a .+−. connection, inwhich case each panel may be connected in parallel, or for purposes ofconnecting panel to a like panel, on any of the sides of the panel.Thus, if the same sides of two panels are intended to be connected; oneconnection would be set to positive, and the other to negative.

E. Solar Collection Module

In some embodiments, the panels may be a square, rectangle or anotherpolygon. FIG. 13A depicts a exploded perspective view of a solar panelaccording to one embodiment. According to these embodiments, a solarpanel has four or more sides configured for being selectively connectedto the same or different-sided solar panels. In FIG. 13A a solar panel100 has six sides and thus takes the shape of a hexagon or hex. FIG. 13Bshows an assembled perspective view of panel 100. Panel 100 includes alens layer 102 that has a plurality of linear concentrators (e.g.,fresnel linear lenses, cylindrical linear lenses or TIR linear lenses asdiscussed earlier). Layer 105 supports the PV strips, which may beorientated relative to a line of focus 103 for the lenses of lens layer102. In some embodiments a hex panel has linear concentrators. In otherembodiments, a hex panel does not have linear concentrators.

Returning to FIG. 13A, panel layer 105 may be a frame layer supporting amovable support layer for PV strips (not shown). In this case, the PVstrips may be linearly shifted relative to the lines of focus of thelens layer 102 (e.g., FIGS. 11-12), or the layer 105 may be the supportlayer in which case the PV strips are fixed in position, e.g., the panel100 corresponds to an embodiment of a static panel as depicted in FIGS.10A-10B, or PV strips are fixed in position and panel 100 is coupled toa tracking mechanism. In this context, “tracking” may refer to eithermaintaining the surface normal parallel to the light rays (as before),or so-called partial tracking in which the sun's motion is tracked onlyin one direction, e.g., sun's motion that is perpendicular to a line offocus for the linear concentrators depicted in FIG. 13A.

In regards to a static panel that provides an increase in the acceptanceangle, panel 100 may have different spatial frequencies between the PVstrips and lens axes, as described earlier. In other embodiments, panel100 may have PV strip spatial frequencies that are the same as the lensaxes' spatial frequencies (or have all PV strips located at the sameposition relative to the lens axes) yet when assembled as a part of asolar collection system still provide 1-D and/or 2-D increase in anacceptance angle. For example, a first panel type can have its PV stripslocated to the left of a lens axis of symmetry; a second panel type canhave its PV strips located to the right of a lens axis of symmetry; anda third panel type can have its PV strips located coincident with a lensaxis of symmetry. According to this embodiment (assuming each panel axisis along the East-West direction and the panels are all directed andfixed at the celestial equator direction in the sky), the PV material inthe first panel may receive the most focused light during the summersolstice the second panel's PV material would receive the most focusedlight during the winter solstice, and the third panel's PV materialwould receive the most focused light during the equinox. The threepanels may be manufactured as separate panel types, or three of onepanel type having three settings may be used. In either case, three ormore panels are connected to each other to provide a static solarcollection system. Accordingly, in a method for assembling a staticsolar collection device, the steps may include selecting differentspatial frequencies or selecting different locations relative to an axisof symmetry (as discussed earlier) and then assembling a panel accordingto these specifications. In an alternative method, a first, second andthird (or more) types of panels are constructed and then assembledtogether (or one panel with multiple settings) to provide a static solarcollection system.

F. Hexagonal Solar Module

Panel 100 has six sides 105. Referring to FIG. 13B, there is shown threeof these sides, 105 a, 105 b, 105 c, each having a an electricalconnector 97 a, 97 b and 97 c respectively. Sides 105 also may include aconnector structure for connecting to another hex panel. Each side 105may have both a male and female connector type so that any side 105 ofone panel 100 may be connected to any other side of an identical paneltype. Further, when sides of two panels are engaged with each other, theconnectors 97 may be automatically placed in abutting contact, such asby mounting the connector face on spring-biased mounts (i.e., biasedoutwardly from the panel side 105) such that when the sides are broughttogether, e.g., by sliding one panel into contact with another, orpushing one face/side 105 into another, the connectors 97 are pre-loadedto press into each other while the panels remain connected to eachother. The connectors 97 may include multiple connector types, e.g.,selectable positive or negative current flow connectors, power connectorand connector for controlling the linear position of PV strips relativeto lenses, output power signal or solar flux indicator (for monitoringwhether there is an optimal position of PV strips relative to lenses orpanel orientation relative to the sun).

The solar panels or modules of the embodiments set forth in thedisclosure may be mounted in a variety of fashions. For example, the hexpanel 100, or a square/rectangular or circular panel of otherembodiments that incorporate principles of the disclosure may be mountedon roofs as roof tiles, or other structures that provide an unobstructedline-of-sight to the sun's path over the sky throughout the year. Thismay be a slanted or flat roof, a side of a building, etc. Sometimes itis difficult to position solar panels during installation so that theyare orientated in an optimal position for collecting solar energy (i.e.,in a position that does not become shaded during part of the day);individual panels may be difficult to replace when repairs are needed;or the available space limits the number of panels that can be safelymounted. Further, the available space for the panels may not beorientated so that a panel, especially a panel having linearconcentrators for focusing light, can be positioned properly withrespect to the sun's path because of limited space or the size of thepanel(s). In other words, the panel axis does not lie within theecliptic plane.

Referring now to FIGS. 14A and 14B, there is shown a top view of severalhex panels connected together to form a solar collection unit 110, and aportion 111 of the solar collection unit 110, respectively. As can beappreciated, since each of the panels 100 may be connected to any one ofthe sides of other panels, in any orientation, there is a greatdiversity of configurations for a solar collection unit that are made upof panels that have greater than four sides, such as a hexconfiguration. This may be desired as it can allow a user to make themost use of available space. Indeed, a hex may be preferred over asquare or rectangle for this reason.

When a hex is used in combination with linear concentrators, there isanother advantage. If the path of the sun relative to the panel mountingspace allows a square or rectangular panel with linear concentrators tobe aligned perfectly, i.e., so that the panel axis lies within the planeof the sun's daily path, or it is 90 degrees from the panel axis, thenthe panel can be easily aligned and all available space used because thepanels can be placed side-by-side. However, if the space is orientatedat an acute angle, e.g., 30, 45, 60 etc. degrees, relative to the planeof the sun's path (as if the panel was rotated about its normal axisP.sub.n in FIG. 7), then it may be difficult to orient thesquare/rectangular panel so that the panel axis is orientated correctly.And even if this could be done, there could be unused space for placingsolar panels. The angular orientation needed for alignment wouldprohibit some panels from being placed because there was insufficientspace.

For example, a square roof will be used to mount square solar panelshaving linear concentrators (i.e., single-axis, or static panelsaccording to the above embodiments). If the sun's path is at 30 degreesrelative to panel (i.e., 30 degrees rotation about axis P.sub.n in FIG.7), then the panels must be orientated at 30, 150, 210, or 230 degreesso that the line of focus for the linear concentrators follows the pathof the sun from sunrise to sunset. This results in wasted roof space forthe square panels, and probably a special mounting, or additionalsupports are needed in the roof so that the panels can be oriented at 30degrees (as opposed to 90 or 0 degrees) and safely supported.

When panels having linear concentrators are arranged as hexes 100 thereare three different angular orientations available (60, 120, 180), asopposed to only two (90 or 180) when a square or rectangle is used.Thus, a hex panel is more versatile than a square because it can bepositioned in an additional angular orientation without there beingunused space, or without requiring a customized mounting arrangement toaccommodate a roof/wall that is not ideally faced towards the sun (e.g.,the broad side of the roof does not face north/south). Hexes 100 may beeasier to mount than squares or rectangles. For instance, for ahex-shaped mounting frame, a single mounting position for rooftops mayaccommodate a greater variety of roof positions (relative to the sun)than a square type mounting frame. If the proper orientation of thepanel axis is at an angle to the direction in which structural membersof the roof or wall are orientated (e.g., frames, studs, or other hardpoints for mounting the panel mount), then it may be difficult toproperly orient a four-sided panel because additional support would haveto be added, or a specialized mount made so that the four side panelcould be arranged at an angle such as 30, 60, or 120 degrees relative tothe horizon. However, with a hex panel 100 configuration, the samemounting scheme can be used for a greater variety of roof positionsbecause there is three different positions available for the same roofmounting scheme. This feature is depicted in FIG. 14B. As shown, eachhex may be rotated among 6 different positions, i.e., a 0, 60, 120, 180,240, and 300 degree position. In other embodiments a circular panel typeallows almost any orientation for the panel axis without having tore-configure the panel mount on the surface of the building or home.

In other embodiments, panel 100 includes 2-D concentrators. Theseembodiments include embodiments in which panel 100 is capable ofincreasing an acceptance angle in two directions. By orientatingmultiple panels among 60 degree angle increments, the panel can in morecases be closely aligned along one of two orthogonal axes thatcorrespond to a spatial frequency axis for PV cells/concentrators than apanel having four or less connecting sides.

G. Portable Solar Collection

A solar panel incorporating one or more of the foregoing embodiments mayalso be configured as a portable solar panel. A portable solar panel mayallow a significant reduction in the storage, transportation andmounting of solar panels to a roof or exterior wall. In otherembodiments, a portable solar panel be used for camping, hiking or otheroutdoors activities, as an emergency power source for automobiles whenthere is a breakdown, e.g., recharge an automobile battery, etc.

Referring now to FIGS. 15A-15C, there is depicted a partial schematicrepresentation of a solar panel according to an additional aspect ofdisclosure. Solar panel 120 is composed of individual, interconnectedsolar collecting elements 122. Each of these elements includes a linearPV strip, e.g., PV strip 11, secured to a linear parabolic lens 123.According to these embodiments, the PV strip 11 is arranged at thelocation of TIR for the parabolic element, as discussed previously inconnection with the embodiments of FIG. 7 or 10B. Each of these elementsincludes a hinge connector 121 a, 121 b located at opposite ends. Thehinges 121 may be easily snapped to mating hinges of other elements toform a foldable solar panel 120 as depicted in FIGS. 15B and 15C. Thehinges may alternately be living hinges. Further, the solar panel 120may be assembled from a kit by snapping together each of the elements attheir hinge points, and then connecting output terminals to a centralbus for current collection.

The width (d) of each element can be between 5-10 mm or any otherdimension. The elements rotate between a stowed (or rolled-up) to adeployed configuration with hinges that permit rotation through an angle.PHI. (see FIG. 15C). Although not shown, it will be understood thateach element 123 (or kit) may also include a lower cover that containsthe necessary electrical connections for connecting each PV strip to aneighboring strip, and also to protect the electronics inside fromdamage. The cover may be fluid impermeable and sufficiently rugged sothat the panel may be used in a wide variety of outdoor environments.

H. Additional Examples of Static/Dynamic Panels & Solar CollectionDevices

Referring to FIG. 16A, a solar collection device 200 may includeconcentrators 202 configured for focusing refracted light onto PV strips11. According to some embodiments a solar collection device may beconfigured for increasing an acceptance angle in a direction transverseto the lens axis of the cylindrical type lens depicted in FIG. 16A. Insome embodiments this may be accomplished by configuring the panel as astatic panel and in other embodiments by configuring the panel as adynamic panel. As an example of these embodiments reference will befrequently made to rod lenses having a circular cross section. However,it will be understood that the same principles apply to other linearconcentrator types. As explained below, one advantage of a circularcross-section is that the individual rod lenses may be packed closelytogether when rotated to follow the sun, since the circular geometryallows each to rotate relative to a neighbor without interference.

Referring to FIG. 16B, a frontal view of three rod lenses 202 shows thatthe direction of the solar rays R1, R2, R3 are at an angle .theta. tothe vertical. In this example the PV material is secured to the bottomof the lenses 202, so that when the lenses 202 rotate so does the PVmaterial. According to this embodiment, the lens elements 202 may berotated as shown, thereby pointing the PV material 11 towards thedirection of the light rays R1, R2, R3. This rotation may beaccomplished by applying a torque T.sub.o about an axis as shown in FIG.16B. This axis may be coupled to a linkage mechanism, such as opposedlinkages 204 a, 204 b and 206 a, 206 b configured to rotate each of thelens elements through a corresponding angle .theta. by displacement ofarms 204 b, 206 b in opposing directions .+−.x (as shown). The lensesmay therefore have annular, or partially annular flange formed at theirends that mate with grooves in arms 206 b, 204 b so that the lenses 202may roll between the displacing arms 204 b, 206 b.

FIGS. 16C and 16D depict two embodiments of a rod lens and PV materialassembly. In each case solar rays originate from directly overhead.However, the concentration factor for the lenses is different. In thisparticular example, the difference in concentration factor is attributedto a difference in the index of refraction between the material used,i.e., the lens in FIG. 16C has an index of refraction n=n1, and the lensof FIG. 16D has an index of refraction of n=n2. The ratio of the lengthover which the light is received (in this case, the diameter of acircle) to the length over which the focused light is distributed on thePV material (c1, c2 respectively) is the concentration factor, e.g., theconcentration factor for the lens in FIG. 16C is diameter times (1/c1).

As depicted in FIG. 16C the length c1 is smaller than the length “d” ofthe PV material, whereas in FIG. 16D d=c2. The former relationship(c1<d) may be used to provide a static panel that has a largeracceptance angle, as opposed to a condition in which d=c. When c=d,e.g., as depicted in FIG. 16D, a dynamic panel, e.g., the panelembodiments just described in connection with FIG. 16B may be used. Inthe case of a static panel, as the sun's position changes the focusedlight continues to focus on PV material because d>c1. In the case of adynamic panel, the lens must be rotated as the sun's position changesbecause d=c2. The condition of d>c may be expressed indirectly as an“Exposure-to-Collection Ratio” (ECR) for a panel. The ECR is intended tomean the ratio of the exposure area, e.g., c1, to the collection area,e.g., d. Thus, in the example depicted in FIG. 16C the ECR would bec1/d<1. The ECR varies inversely with a static panel's acceptance angle.

In the embodiments of the static or dynamic lenses discussed inconnection with FIG. 16 the rod lenses 202 may be made from suchmaterial as glass or plastic. The lenses may be solid or glass orplastic tubes, or hollow circular tubes that are filled with atransparent liquid which acts as a dielectric. The liquid may becirculated through the center of the lenses to also serve as a heatsink.

In some embodiments, a solar panel may be arranged so that the panel issubstantially translucent. For example, the solar panel 300 depicted inFIG. 17A has a series of rod lenses 302 supported by a frame structure308. This panel may be configured such that it appears essentiallytranslucent since there is no opaque substrate located beneath the rodlenses. The frame assembly 308, which includes parts 305, 308 a, 308 bsupport the concentrators 302 at essentially their peripheries so thatdiffused light may pass through the panel. This will cause the effect ofthe panel blending into its environment more, so that its presence isnot as noticeable. For instance, if the panel sits atop a roof, thepanel will tend to blend into the roof design more so that it is not asnoticeable to someone looking at the roof. In some embodiments, thesupport 308 may be thought of as suspending the concentrators above therooftop.

The frame support may be configured for supporting a static panel ordynamic panel design, as discussed earlier in connection with FIGS.16A-16D. In FIG. 17A a dynamic panel is depicted. Frame 308 includes, atthe nearest ends of the concentrators 302 in FIG. 17A a housing 308 awithin which there is a coupling 306 a to a rotary motor or drive 306 bfor rotating the concentrators about their longitudinal axes as thesun's apparent position changes. The coupling (e.g. FIG. 16A and relateddiscussion) supports the concentrators 302 at one end. At the far endthere may be a similar coupling for driving the concentrators or ahousing assembly that receives a post formed at the end of each of theconcentrators. This support which permits free rotation of theconcentrators about their axes while supporting in the translationdirections.

Between the ends 308 a there may be mid-span supports 305 for theconcentrators 302. These mid-span supports may include, or form cleaningor sweeping strips that can sweep or clean the surface of theconcentrators 302 when the concentrators 302 are rotated to follow thesun. Referring to FIG. 17B, which shows a portion of a frontal view ofthe panel 300, the mid-span support 305 are configured to have cleaningor sweeping strips 305 a located at positions that do not interfere withthe collection of solar energy, and on each side of the concentrators302. A surface-contacting portion 309 (e.g., a rubber-like material,Teflon, brushes) slides over the outer surface 302 a of the concentrator302 to essentially sweep the surface free of debris. As the linearconcentrators 302 rotate through an angle .theta. to follow the path ofthe sun, the contacting surface of the cleaning strips 303 a slide overthe corresponding length of the outer surface 302 a (i.e., arc length“A” depicted in FIG. 17B) of the linear concentrators, therebyautomatically sweeping the surface free of any dirt, dust or water thatmay accumulate. The cleaning strips 305 can reduce the frequency inwhich the panel may need cleaning to maintain the panel's efficiency.Thus, in the embodiments in which a dynamic panel is selected, thecleaning strips 305 may be added to assist with cleaning the surface ofthe concentrators without little added cost or complexity. Further, thestrips 305 present a solution to the need for frequent cleaning of panelsurfaces that are in hard-to-reach places or exposed to relatively largeamounts of dust or dirt.

In some embodiments, the drive assembly 306 b and associated programming(i.e., daily, seasonally, etc.) for following the sun may include anadditional cleaning cycle. In these embodiments, the motor or drive mayrotate the concentrators through a 180 degree angle for cleaningpurposes, e.g., at nighttime. In some embodiments, the frame may alsoinclude a cleaning solution, or simple water that flows over thecleaning strips to assist with removing debris or dirt from the surfaceof the concentrators 302.

In some embodiments, the solar collection device may include a cover onall sides, one side, two sides, e.g., opposing sides, or no covers atall. As will be appreciated, there are advantages and disadvantages ineach case and depending on the application, there may be a preferencefor having covers completely or partially covering the solar collectiondevice, or no covers at all.

As mentioned earlier, a panel 300 according to the disclosure may beconstructed so that it appears essentially translucent when viewed frompositions outside of the direction where light collects on the PVmaterial. In other embodiments, the solar panel may include acombination of translucent structure, and opaque, semi-transparent,and/or patterned surfaces to provide an aesthetically pleasing,intriguing or eye catching appearance to a structure, e.g., a rooftop ofa home or building. The patterns or designs may be formed over theunused portions of the concentrators, i.e., the portions of theconcentrators which do not focus light onto PV material.

Referring to FIGS. 18A-18B, there is depicted examples of this aspect ofthe disclosure. Referring to FIGS. 18A, 18B a rod lens 302′ of analternative embodiment of panel 300 includes an opaque pattern or image330 formed on the unused portion of this cylindrical lens. The patternmay be formed on the concentrator by painting, etching, or a variety oftechniques for creating a desired shape or appearance to theconcentrator when viewed outside of the direction where light iscollected on the PV material. FIG. 18B shows a perspective view of theconcentrator 302. The type of pattern is indicated by patterns 330 a,330 b. The surface area occupied by the pattern may be determined fromthe range of angles where light is expected to be collected and focusedonto the PV material, as indicated by the angle .OMEGA., i.e., the leftand right extremes where solar energy is collected by the lens.

In one example, the pattern on a concentrator may be the same asadjacent concentrators (e.g., a color complimentary to the roof color).In some embodiments, the pattern may be chosen to portray a message,display, e.g., a flag, to serve as an advertisement, i.e., a brand name,or to simply reflect a pleasing pattern. In some embodiments, multiplepatterns may be provided when a dynamic panel is used. For instance, thearrays of concentrators 302 depicted in FIG. 17A may have a pattern 330(FIG. 18A) formed on the unused surfaces of the lens, including a firstpattern 330 b and second pattern 330 a formed on the left-hand-side ofthe PV material 11 (FIG. 18A), or on both the left and right hand sidesof the PV material 11. [00136] FIGS. 18B and 18C show how such a panel300 may appear to an onlooker at different times of the day. The panel300 is shown mounted atop a slanted rooftop and is visible to a person(as shown). In FIG. 18C the sun has a first apparent position in the skyoverhead, e.g., noontime sun, while in FIG. 18D the sun has a secondapparent position in the sky, e.g., late afternoon. When the sun changesits position, the panel 300 (a dynamic panel) will rotate theconcentrators 302 in unison so as to keep the PV material facing thesun. When this rotation has occurred, the person viewing the roof willnotice a change in the pattern created by the array of concentrators.For the sun position depicted in FIG. 18C, the person will only seepattern 330 a. When the sun as moved closer to the horizon (FIG. 18D)the concentrators rotate, which causes both pattern 330 a and 330 b tobecome visible to the onlooker. In another embodiment, the panel may beconfigured so that a pattern, e.g., pattern 330 a, becomes visible tothe onlooker only later in the day. Before that time, the panel 300appears to blend into the roof color or pattern. Thus, the disclosurealso encompasses dynamic solar panels that may provide aestheticallypleasing designs, serve as a late day advertisement (e.g., pattern 330a, when it becomes visible displays in the aggregate over allconcentrators an advertising slogan, brand, image or message)

According to another aspect of the disclosure, a solar panel isconfigured for being disposed over windows. In some embodiments, thesolar panels may be static or dynamic panels, as described above, andmay be positioned to cover windows, or be incorporated inside a window,and function as Venetian blinds or coverings that allow diffused lightto pass through. Such placements of solar energy collectors may beespecially advantageous at areas of high or low longitudes, i.e., faraway from the Earth's equator, where the sun travels close to thehorizon. For instance, a solar panel, e.g., one constructed in a mannerconsistent with panel 300 and discussed in connection with FIG. 17A,that is located in the northern hemisphere (latitude of about 35) andmounted over south-facing windows of a high-rise building collectsroughly 70 percent of a roof mounted panel of the same size over thecourse of a year. Such a mounting is depicted in FIG. 19. Theconcentrators 302 are arranged to extend from ground level upwards butmay also be arranged to extend horizontally. For the embodiments inwhich the solar panel 300 is translucent (as discussed earlier), thepanel 300 may cover the window continuously. As the sun comes into view,only diffused light passes through the panel 300, while the direct lightis collected at the PV material.

In the embodiments of a solar collection device utilizing a linearconcentrator the panel axis may be orientated east-to-west,north-to-south, or indeed in other directions depending on the locationof, and/or optics used in the solar collection device, or based on otherreasons. In the examples discussed above and depicted in the drawings,e.g. FIG. 5A, reference has sometimes been made to solar collectiondevices in which the panel axis was orientated to face east-to-west.However, it will be understood that the various aspects of thedisclosure discussed above in connection with solar collection deviceshaving 1D concentrators apply equally to collection devices in which thepanel axes are not orientated in an east-to-west direction. Thus, thedisclosure is not limited to collection devices with 1D concentratorshaving panel axes intended to be orientated east-to-west.

I. Other Examples

FIGS. 20 and 21 depict embodiments of a solar collecting element 302having a circular cross-section rod lens 304 with a PV strip 311attached to the lens 304. Referring to FIG. 21A, showing a close-up viewof the collector of FIG. 20, the PV strip 311 may be attached to thelens by an index-matching glue. The PV strip 311 includes the PVmaterial 312 and current conducting metal grid. In some embodiments, thePV material may be secured to a rod lens by chemical vapor deposition,evaporation, electroplating, or other suitable manufacturing techniques.The PV strip 311 may be secured to the outer surface of the rod lens304, or secured to a pre-formed groove in the rod lens 304 (see FIG.21C).

FIG. 21B depicts an embodiment in which TIR reflectors 316 are disposedover the portions 314 of the metal grid 312 in the collection plane. TheTIR reflectors 316 a-316 b may be fabricated as part of the PV strip311, e.g., as depicted in FIGS. 3-4, or formed into the rod lens portion304 a that receives the PV strip 311. As discussed earlier, the TIRreflectors 316 reflect solar energy away from the metal grid 316 andtowards the PV material 312. Refracting lenses may be used in place oflenses arranged for TIR, as discussed earlier in connection with FIGS.3-4. For the embodiment depicted in FIG. 21B, the TIR reflectors arereceived within grooves formed along the outer surface of the rod.

FIG. 21C depicts another embodiment of a solar collecting elementincluding a circular rod lens with attached PV strip. According to theseembodiments, a groove 304 c may be formed along the outer surface of thelens. The metal grid 316 and PV strips 311 may then be placed within thegroove 304 c, e.g., with a suitable adhesive. In some embodiments, theconcentrator according to FIG. 21C may include a TIR reflector such asdepicted in FIG. 21B, or an assembly in accordance with other examplesof refracting and/or reflecting structure adapted for redirecting lightfrom a metal grid towards the PV material as discussed previously inconnection with FIGS. 3-4.

FIGS. 22A-22D show ray traces for a solar collection device having aseries of rod lenses 302 arranged parallel and side-by-side (examples ofsuch a solar collection device are discussed in more detail inconnection with FIGS. 16 and 17, above). Referring to FIG. 22A, this raytrace was calculated based on the optical properties of the collectingelement depicted in FIG. 21B. The effect of the TIR reflectors isevident in this ray trace. At the edges the light which would normallybe received at the metal grid is reflected towards the PV material.

A ray trace for a series of collecting elements placed side-by-side isshown in FIG. 22B. In this example the light source is located directlyabove the PV material. FIG. 22C shows a ray trace when illumination isat 45 degrees from normal in the plane defined by the rod lens 304longitudinal axes. FIG. 22D depicts a ray a trace for collection devicein which the rod lenses are rotated about their longitudinal axes. INthis case the light source is also at 45 degrees form normal. As can beseen, the PV strips are maintained in focus when the light source is at45 degrees from normal.

FIG. 23 depicts an example of a static collection panel having the PVstrips arranged according to a spatial frequency. In accordance with theprinciples discussed in connection with FIGS. 9A-9B, the orientations ofthe PV strips about the lens longitudinal axes (lenses 302 have PVmaterial located at different angles about the lens longitudinal axis)provides the collection device with PV material that is in focus for onepart of the day, and not in focus for another part of the day. In thisway, there may always PV material in focus for collecting solar energy,without tracking the panel.

FIG. 24A depicts embodiments of solar collection elements in which a rodlens of circular cross section is cut to remove unused portions of thelens (i.e., the portions of the lens which are not used to focus light).For instance, in FIG. 24A there are cut-outs 322 a, 322 b. The portionof the lens removed at these locations are not used to focus light (seeray traces in FIG. 22). It may be desirable to make such cut-outs as away of reducing the weight of glass rods in a panel. It may also bedesirable to make such cut-outs to enhance the transparency of thepanel.

In FIG. 24B the cut-outs are made in such a manner as to create TIRreflectors for the solar collecting element 330. Sides 322 a, 322 bextend down to form a more narrow collection plane. Such a design cancreate a factor of two increase in the concentration ratio due to TIR,e.g., from 5 to 1 to 10 to 1, in addition to weight reduction andenhanced translucency of the panel. Use of the word “cut-out” is notintended to indicate that one manufacturing or forming method should beused over another, or that other methods for forming the lenses depictedin FIGS. 24A-24B are outside the scope of the invention. Forming“cut-outs” is only a presently preferred method for making lenses inaccordance with the principles disclosed in connection with FIGS. 24Aand 24B.

FIGS. 25A-25B depicts examples of a solar collection panel 340 having acircular perimeter formed by rod lenses 302 arranged side by side.According to this embodiment, the rod lenses may be fixed relative toeach other, i.e., they do not rotate about their longitudinal axes.Instead, the panel is rotated about axis A as the sun's apparentposition changes. The mechanism for rotating the panel may be locatedbeneath the panel and coupled to a sun positioning element to rotate thepanel in accordance with the sun's movement. As compared to a panel thatrotates about the one or both axes perpendicular to axis A to track thesun, rotation of the panel 340 about axis A may be more easilyimplemented (from the perspective of the mechanism used to turn thepanel, installation and locations in which the panel may be mounted).FIG. 25B depicts a solar collection array 350 made up of a collectionpanels 340. The panels 340 may be rotated in unison as the sun'sapparent position changes by rotation of each of the panels 340 groupedtogether as shown.

While particular embodiments of the present invention have been shownand described, it will be obvious to those skilled in the art thatchanges and modifications can be made without departing from thisinvention in its broader aspects. Therefore, the appended claims are toencompass within their scope all such changes and modifications as fallwithin the true spirit and scope of this invention.

1. A solar collection device, comprising a concentrator having anexposure area; and PV material having a collection area; wherein thecollection area is greater than the exposure area.
 2. The solarcollection device of claim 111, wherein the concentrator is a rod lens.3. The solar collection device of claim 111, wherein the exposure areareceives refracted light.
 4. A non-tracking solar collection system,comprising: concentrators positioned relative to PV material such thatat least a portion of the light collected by the concentrators isdirected at PV material, wherein the acceptance angle for the solarcollection device is such that the at least a portion of the collectedlight directed at PV material is approximately constant as the sun'sapparent position changes.
 5. The non-tracking solar collection deviceof claim 114, further including a means for increasing the acceptanceangle including configuring the concentrators for rotationaldisplacement as the sun's position changes.
 6. The non-tracking solarcollection device of claim 115, wherein the PV material rotates with theconcentrator.
 7. The non-tracking solar collection device of claim 116,wherein the concentrator approximates a cylindrical lens formed as arod.